Don't Eat With Your Mouth Full

Where can we live but days?

Is there a term in common use to distinguish fics consistent with canon (e.g. "Neville and his Grandmother Pack his Bags the Night before he first goes to Hogwarts") from those that contradict it (e.g. "After the Final Victory of the Death Eaters, Draco decides to Employ Ron Weasley as his Houseboy")?

Not many simple terms, but "Starts in S5 canon but goes rapidly AU" is one I see quite often (many variations, obvs). I've seen "off-canon" a few times but don't really like it. "[A canon event] never happened" is another.

Canon-compliant is good. "Doesn't comply with[comics, a given series/episode/book]" is fairly common.

"S" stands for "season" of a TV show. (You may have noticed that's what I write.)

In a fandom based on TV, a sequence of films or a long sequence of novels it is also common to use initials for a specific point from which the fic springs off. Thus, a story based on "What if Spike had killed Wood in LMPTM?" Or "How Philippa might have got home at the end of PiF", or " Boromir survived the orc attack in TTT". Code because fanfic is mostly consumed by people with very significant shared knowledge and thus easily recognise references. ("Buffy the Vampire Slayer ", Dorothy Dunnett's Lymond stories and " The Lord of the Rings" in the unlikely event that you didn't recognise any of those references.)

Yes, and AU generally means wildly different to canon - I write a LOT of AUs (whichever fandom I'm in!) - often historical ('cos that's my thing). But I do also write canon divergences where the story jumps the tracks at a particular point in canon, and goes off and does its own thing (or the characters do! *rolls eyes*)